Communications connectors, where communication lines are connected to each other and to network devices, represent an increasingly important aspect of the communications industry. Communications connectors may include pairs of conductors which are used as connection terminals for conductive twisted-pair communications cables. Though connectors are necessary parts of a communications connection, they introduce a certain amount of signal degradation into communications signals. One type of signal degradation introduced by a connector is near-end crosstalk (NEXT), an error signal resulting from interference between pairs in the connectors, with the error signal propagating backward from the direction of signal flow into the connector. Far-end crosstalk (FEXT) is similarly caused by interference between pairs and propagates in the direction of signal flow through the connector. A third type of signal degradation, return loss (RL) represents reflection of signal backward from the connector due to impedance mismatches. Insertion loss is a fourth type of signal degradation that represents signal loss through the connector in the direction of signal flow.
As the bandwidth of communications rises, the need for high-quality communications connectors meeting tight requirements for reducing these types of signal degradation increases. Concurrent with the increasing demands on connector quality, the need for consistent testing of connectors to verify their suitability is increasing. One method for detecting the amount of signal degradation introduced by a connector is to analyze a connector using a network analyzer. A network analyzer contains a transmitting port, which sends a test signal through a connector or other device under test (DUT), and a receiving port, which receives signal from the connector. Electronics within the network analyzer analyze the returned signal relative to the transmitted signal and generate information about NEXT, FEXT, RL, and insertion loss sufficient to determine the suitability of the connector.
Though network analyzers are accurate, they have significant drawbacks. One drawback of network analyzers is their speed. One NEXT test in a common network analyzer takes approximately three seconds, and six tests must be performed for each eight-conductor connector (one test each for conductors one and two, one and three, one and four, two and three, two and four, and three and four). Thus, even assuming zero time for changing pairs under test, a single connector will take eighteen seconds to test for NEXT using a network analyzer. Because the time delay for testing using a network analyzer is longer than the time for production of a connector, production line testing of all manufactured connectors using a network analyzer is impractical.
Another shortcoming of connector testing using network analyzers is that network analyzers generally operate in the common mode of signal transfer rather than in a differential mode. Communication connectors are generally designed to work in a differential mode. This difference requires the use of a balun when testing connectors using a network analyzer. A balun is a device that converts a common mode signal to a differential mode signal, and it adds a certain amount of noise and error into the test results.
Because of these and other shortcomings of current connector test devices and methods, there exists a need for a fast and accurate test procedure and system for analyzing communication connectors.